The present invention relates to medical diagnostic ultrasonic imaging, and in particular to improved methods used in connection with the combination of two or more partially overlapping images into an extended field of view image.
Hossack et al. in U.S. Pat. No. 6,014,473, filed Aug. 22, 1997, assigned to the assignee of the present invention and hereby incorporated by reference in its entirety, describe systems for acquiring, aligning and registering multiple medical diagnostic ultrasound images. Such alignment is used both to determine the motion between two selected images as well as to provide the information needed to composite an extended image from two or more selected ultrasound images. That is, two coplanar tracking images can be aligned and in this way the relative motion of the transducer between the times of the two tracking images can be obtained. Similarly, two or more substantially coplanar diagnostic images can be aligned and then composited to form an extended field of view.
In one embodiment, Hossack et al. disclose adaptively determining the number of image data frames that are collected between consecutive tracking frames (column 22, lines 18-50). The number of image data frames collected between tracking frames varies in response to the estimate of motion between each image data frame.
The collected frames are compounded. The compositing method described in U.S. Pat. No. 6,014,473 interpolates data from boundary portions of different image data frames with variable weights (column 29, lines 5-22). The weights applied to the image data frames vary linearly as a function of distance where the weights for one frame are one minus the weights for the other frame. Using these weights, a previous frame is compounded with a subsequent frame. The composition of the previous frame is not discussed, but Hossack et al. note that compounding can be used for accumulating image data.
Likewise, Weng et al. in U.S. Pat. No. 5,575,286 disclose a xe2x80x9cramp compoundingxe2x80x9d which gives weight ramps for both a new image frame and an existing compound image in the overlapping area (column 8, lines 21-30). Weng et al. do not discuss the composition of the existing compound image. Weng et al. also disclose alternatives to the ramp compounding, such as using only new pixels for non-overlapping regions or recursively averaging the new image frame with the existing compound image.
The present invention is directed in part to an improved compounding method that provides versatility and is quick to execute.
By way of introduction, the preferred embodiments described below provide methods and systems for combining multiple frames of data for an extended field of view. Using finite-impulse response combinations, adaptive compounding or combinations thereof, the amount of speckle is reduced, and/or the signal-to-noise ratio is increased for the extended field of view images.
The present invention is defined by the following claims. This paragraph has been provided merely by way of introduction, and is not intended to define the scope of the following claims.